doc: release notes: add Fast Pair nRF53 PM deprecation changelog entries

Add changelog entries for the Fast Pair Locator Tag nRF53 PM-to-DTS
migration:

- Bluetooth Fast Pair samples: note the migration of the
  nrf5340dk/nrf5340/cpuapp and thingy53/nrf5340/cpuapp board targets
  from the deprecated Partition Manager to the devicetree (DTS)
  partition layout, and the removal of the corresponding /ns board
  target variants from the sample.
- Google Fast Pair integration: note that the integration guide no
  longer carries the nRF53-specific Partition Manager exception, so
  the Partition Manager is fully deprecated for the supported Fast
  Pair project configurations.

Ref: NCSDK-38010

Signed-off-by: Kamil Piszczek <Kamil.Piszczek@nordicsemi.no>

Author: kapi-no

doc/nrf/releases_and_maturity/releases/release-notes-changelog.rst

@@ -328,6 +328,12 @@ Bluetooth Fast Pair samples
 
   Support for this target was already dropped during the IronSide SE migration in the |NCS| v3.1.0 release.
 
+* :ref:`fast_pair_locator_tag` sample:
+
+  * Updated the configuration of the nRF53 Series board targets (``nrf5340dk/nrf5340/cpuapp`` and ``thingy53/nrf5340/cpuapp``) by migrating from the deprecated :ref:`partition_manager` to the devicetree (DTS) solution that is used for defining the partition layout.
+    All board targets supported by the sample now use DTS for partition definitions.
+  * Removed the ``nrf5340dk/nrf5340/cpuapp/ns`` and ``thingy53/nrf5340/cpuapp/ns`` board target variants from the sample's configuration.
+
 Cellular samples
 ----------------
 
@@ -626,7 +632,8 @@ This section provides detailed lists of changes by :ref:`integration <integratio
 Google Fast Pair integration
 ----------------------------
 
-|no_changes_yet_note|
+* Updated the :ref:`Google Fast Pair integration <ug_bt_fast_pair_integration>` guide to reflect that all supported board targets use devicetree (DTS) for partition definitions.
+  The :ref:`partition_manager` no longer has any Fast Pair-specific exception and is fully deprecated for the supported Fast Pair project configurations.
 
 Edge Impulse integration
 ------------------------